Large-capacity All-Solid-State Lithium Metal Batteries Based on Chloride Solid Electrolyte

Using inorganic solid electrolyte to replace organic electrolyte is an effective means to improve the electrochemical performance of lithium batteries, improve the safety and reliability of lithium batteries, and extend their service life. Common inorganic solid electrolytes include garnet solid electrolytes, sulfide solid electrolytes and NASICON solid electrolytes. In recent years, chloride-based solid electrolytes have attracted more and more attention and are considered to be the most reasonable choice for large-capacity all-solid-state lithium-ion batteries.

Recently, a research team from Nagoya Institute of Technology reported an all-solid-state rechargeable lithium metal battery based on a chloride solid electrolyte. Researchers prepared a strong solid-solid bond high formability chloride solid electrolyte by cold pressing. This chloride solid electrolyte has close particle contact and high ion migration efficiency and can effectively inhibit the growth of lithium dendrites.

As a counter anion required for conducting lithium ions, chloride ions have a larger ion radius and more extranuclear electrons than oxygen ions, which contributes to the high polarizability and formability of the electrolyte powder. However, not all lithium-containing chlorides are stable and possess high-speed ion conductivity and high formability. So the researchers used first-principles and classical force field calculations as indicators of ion conductivity, formability and thermodynamic stability. They conducted a comprehensive study on the Li⁺ ion migration energy, bulk modulus, and energy above the hull, and finally found a single The indicators of slant LiAlCl₄ (LAC) are low.

Focusing on the monoclinic LiAlCl₄, the researchers prepared a metastable electrolyte through a mechanochemical method, which retains the original monoclinic main structure, and lithium ions exist in part of the conductive path (2.5% of Li occupies all sides of the gap Body position). The impedance measurement shows that the ionic conductivity of the LAC compact is 2.1×10^-5 S cm^-1, which is 20 times higher than that of the traditional solid-state synthetic LAC at room temperature. The electrical conductivity is more than one order of magnitude higher than that of the garnet-type Li6.6La3Zr1.6Ta0.4O12 (LLZT), which is attractive for the use of sintered bodies for Li metal electrodes.

Experiments have shown that the lithium metal symmetric battery using LAC particles shows good cycle performance. When the current density is 0.1 mA cm^-2, the LLZT battery will be short-circuited in the first cycle, and based on this research The solid-state lithium battery made of chloride material has achieved 70 stable charge and discharge cycles.

References: Naoto Tanibata*, Shuta Takimoto, Koki Nakano, Hayami Takeda, Masanobu Nakayama, Hirofumi Sumi, Metastable Chloride Solid Electrolyte with High Formability for Rechargeable All-Solid-State Lithium Metal Batteries, ACS Materials Lett., 2020, 2, 880 –886, DOI: 10.1021/acsmaterialslett.0c00127